In 3D seismic imaging and interpretation of these images, there are a number of commercial software products available for estimating the economic viability of oil and gas exploration; which help determine the viability of exploitation projects. Some of these products utilise thresholding and/or connected component analysis and/or region growing or neural network classification techniques in order to define so-called 3D Geological Elements (or “3D geobodies”).
In non-seismic imaging domains more sophisticated techniques have been developed, some of which have been incorporated into commercial products, and image segmentation is still an active area of research. Two techniques with interesting properties in relation to the seismic image analysis problem are active contours and level sets.
3D geobody delineation techniques that are currently available commercially are computationally simple and unreliable due to the poor contrast and signal ambiguities that commonly occur in 3D seismic data. To overcome these problems the object delineation process needs to combine information extracted from the data with a priori knowledge gained through interaction with a human operator in real time.
Application of active contour based techniques allows this problem to be solved in part by providing a parametric surface representation of such objects of interest (an explicit object representation).
This enables topological knowledge or “constraints” to be integrated into the segmentation process thus “interpolating” the image information where it is corrupted by noise or provides an incomplete representation of an object of interest.
Level Sets (Implicit object representations) are less capable of dealing with noisy, ambiguous or low contrast data, rather than active contours; and so provide less scope for topological constraints and human operator intervention. This is in part due to their implicit nature and computational overheads. However, they can be useful when dealing with topology to changes encountered during a 3D object delineation process which would be computationally hard using explicit techniques.